1. Field of the Invention
The present invention relates generally to terminal clamp assemblies for clamping conductor wires of different sizes to a terminal block. More particularly, the invention concerns an electrical connection terminal assembly that includes a tilt or teetering washer of novel construction that tilts relative to the terminal screw proximate the axial center line thereof.
2. Discussion of the Invention
A number of different types of terminal clamp assemblies have been suggested in the past. Typically, the prior art assemblies comprise a screw and a clamping plate which is loosely mounted on the screw shank for tilting or teetering relative to the shank to accommodate wires of different sizes. Many of the prior art devices incorporate a rib structure at the undersurface of the washer to concentrate a clamping pressure on the conductor wires in an attempt to insure a positive and secure electrical contact.
In certain prior art devices, tiltability of the clamping plate or tilt washer has been achieved by providing a particularly designed clamping surface beneath the head of the screw. U.S. Pat. No. 3,744,012 issued to Gutshall is exemplary of this type of construction. Another prior art construction is described in U.S. Pat. No. 4,310,214 issued Carlson, wherein a clamp plate or washer is provided with four angularly-spaced, raised embossments which project above the upper surface of the clamp plate for engagement with a circular protrusion formed on the undersurface of the head of the screw. In yet another prior device, which is described in U.S. Pat. No. 3,135,777 issued to Barth, the clamping member is provided with a tube like protuberance which terminates in an edge that engages the undersurface of the screw head and permits the washer to tilt about a location disposed proximate the shank of the terminal screw. Other, more complicated and elaborate terminal connector assemblies, are described in U.S. Pat. No. 3,470,526 issued to Joly and in U.S. Pat. No. 3,081,507 issued to Gribble.
The prior art terminal clamp assemblies typically suffer from one or more shortcomings. For example, some are unduly complex, are difficult to use and are expensive to manufacture. Others lack in reliability in that they do not positively grip wires of different sizes. In this regard most electrical terminal clamp assemblies are subject to Underwriters Laboratory requirements. One of these requirements provides that certain terminal clamp assemblies be capable of grasping a 14 gauge wire on one side of the screw and a 22 gauge wire on the other side of the screw. In order to meet this requirement, the washer must tip or tilt substantially relative to the screw so that both the large and small conductor wires are securely clamped. Because the tilt washers in the prior art devices typically pivot about points located closely adjacent the edge of the shank of the screw and closely adjacent the center of the larger wire, the washer often cannot be effectively forced into secure clamping engagement with the small wires.
The device of the present invention uniquely and elegantly solves most of the problems inherent in the prior art devices by designing the tilt washer in a manner so that it freely tips relative to the undersurface of the screw head at locations proximate the axial center line of the screw. This novel construction enables the washer to tilt in a manner to effectively grip both the large and small diameter wires which are disposed on either side of the axial center line. To enhance the gripping abilities of the washer, the undersurface thereof is provided with uniquely configured and arranged gripping projections Which positively and securely grip both the large and small diameter wires.